Unit 3 The Physics of Astronomy: How Motion Affects the Universe

1. Unit 3 The Physics of Astronomy:How Motion Affects the Universe Images from the Hubble Telescope

2. Big Bang Theory • Previously we discussed one theory of how the universe formed, the Big Bang Theory, where all matter and energy was released approximately 14 billion years ago.

3. The Future of the Universe • Two factors influence the future of our universe. • The first… momentum of matter in the expanding universe

4. The Other Future Scenario The 2nd factor for the future … The inward force of gravity These two factors are influencing motion in the universe!

5. Why Study Motion in our Universe? • To know what kinds of observations to make. • To know how to accurately measure these observations. • To know how to mathematically determine measurements of motion. • To understand the relationships between objects with motion and why it occurs rather than just knowing that it occurs.

6. Scientists have been studying motion for over 2300 years! Artistotle, Aristarchus, Ptolemy, Copernicus, Brahe, Galileo, Kepler, Newton & Hubble

7. Feel The Force A force is a push or pull that can cause an object to speed up, slow down, change shape or change direction. You can’t see the force but you can see what it does. Forces act on objects including living organisms (that’s us!) all the time. Friction is also a force that makes objects slow down. How will objects in space be influenced by forces?

8. Let the force work for you! Imagine you are pedaling or pushing your bike up a hill. That push is a force. The result of the force is that the bike moves. If you pedal or push harder with greater force the bike will move faster. Then the bike’s speed will increase. If you were in a race each bike would be traveling at different speeds!

9. The Speed is the rate (how fast) at which an object moves. Does not keep track of direction. Speed = Distance Can be in miles or meters Time Average Speed = Total Distance Total Time Example: 400 miles = 50 mph OR meters per second 8 hrs

10. What is the speed of the Earth orbiting around the Sun? • Earth is also moving around the Sun at about 67,000 miles per hour!!!

11. What is the speed of our Solar System moving within the Milky Way Galaxy? The solar system is about 26,000 light years from the center of the Milky Way Galaxy. Our solar system travels 155 miles per second and travels about 200-250 million years to orbit once around the Milky Way.

12. How Fast Are Objects Moving in the Universe?

13. Which Way Did It Go? Scientists will use velocity to describe how fast something is moving in a particular direction. It is measured in meters per second or miles per second. If we are pedaling or pushing our bike from LHS to the movie theatre at 20 miles per hour the speed would be 20 mph and the velocity would be 20 mph southeast.

14. Velocity • Velocity is the rate at which an object changes its position. • Speed and direction of an object’s motion. • Direction can be: up/down, left/right, to/from , East, West, North or South. • Example: 65 mph EAST

15. Velocity Continued Example: if a person is taking one step forward and one step back-always returning to the original starting position results in zero velocity (the motion never results in a change in position) If you want to maximize velocity, than every step must move that person further from where they started. Equation: Average velocity = change in position ______________ time

16. Measuring change An object can change velocity by changing direction even if it doesn’t change speed. An object can also change its velocity by speeding up or slowing down. If our bike would speed up when we use more force OR slow down when we get tired, OR if we make a left hand turn with our bike we are changing our velocity. Changing velocity is called acceleration.

17. Acceleration is the rate at which an object changes its velocity. It is a rate of a rate! You are accelerating if there is a … change in speed change in direction change in BOTH speed and direction Acceleration = Change in Velocity Time Units of measure: most likely meters/second2 or km/hr/sec or mi/hr/sec

18. Acceleration: Think it Over… • Acceleration has nothing to do with going fast, you can be going very fast and not be accelerating. WHY? • If you slow down at a stop sign and start again are you accelerating? • If you rotate in a circle are you accelerating? • If you slow down at a corner & turn, are you accelerating?

19. Two bike scenarios • Scenario 1: You and your bike are stopped waiting at a light and a person (who looks like the Hulk) hits you with a strong force. You and your bike fall down. What is this concept called? • Scenario 2: You are riding your bike and another bike hits you with a strong force. You and your bike fall down. This concept is the same concept from Scenario 1.

20. Newton’s First Law of Motion = Inertia 1. In regards to motion all matter has two states At Rest OR Moving 2. An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed unless acted upon by an unbalanced force. 3. Things keep doing what they are already doing!

21. Inertia 4. Inertia is the resistance an object has on it’s state of motion. 5. Inertia is a property of matter. 6. The greater your mass then the greater your inertia.

22. Inertia: Think it over… • If I slide a book across the table why does it stop at the rest position? • Is a force required to keep an object going? • An astronaut throws a rock in space far from friction & Earth’s gravity. What will happen? • If you stop a car suddenly what happens to a 80 lb child compared to a 200 lb man?

23. Food Fight Jim and Bob are arguing in the cafeteria. Jim says that if he flings Jell-O with a greater speed it will have a greater inertia. Bob argues that inertia does not depend on speed. • Who do you agree with? • WHY???

24. Roller Coasters! • You probably know that when you ride a roller coaster you need to be strapped in. • WHY? (using science terms)

25. Baseball Throw The ball wants to continue in motion due to… Describe what is happening in the picture. Use 3 science terms

26. What Matters? • You are back on your bike but this time you are carrying an elephant in your bike’s basket and your friend is carrying a puppy in their basket. You both are traveling at the samevelocity but a car zooms out in front. • Who will have a more difficult time stopping their bike? • WHY???

27. What else matters? • This time you and your friend both have a twin puppies in your bike’s basket. Although you are pedaling with more force therefore with more velocity than your friend. A car again zooms out in front of you both. • Who will have a more difficult time stopping their bike? • WHY???

28. Momentum = Inertia in motion 1. Inertia depends on mass 2. Momentum depends on mass and velocity (speed with direction). 3. A masscan have momentum only when its moving. 4. Momentum = mass X velocity or P = mv

29. Momentum’s relationship with mass & velocity • Momentum is directly proportional to mass or is dependent upon mass. • If mass increases then momentum increases. • Momentum is also dependent on velocity. • If velocity or speed increases then momentum increases.

30. Momentum • When an object has more mass OR when an object is moving at a higher velocity it will have more momentum. • Momentum is how forcefully an object is moving in a particular direction. If an object such as an elephant has a lot of mass it is hard to start moving the elephant. But once the elephant is moving it is harder to make the elephant to slow down or stop.

31. Momentum: Think it over… • 1. If velocity decreases what happens to momentum?

32. Momentum: Think it Over… 2. If you were going to be hit by a vehicle both traveling at the same speed which one would you prefer… • a Smart Car or a Hummer? • WHY?

33. Hubble’s Law • According to Edwin Hubble, the Universe is currently expanding and still expanding. • In 1929, Hubble discovered (using spectroscopy) that galaxies are moving away from us in proportion to their distances from us.

34. Visible Light • Visible light is the light you can see and the colors are represented as ROYGBV • When all the wavelengths are viewed together they make white light. • Spectroscopy uses only visible light from objects in space.

35. Each color has a different wavelength Violet has the shortest wavelength and highest energy Red has the longest wavelength and lowest energy Spectroscopy

36. Hubble’s Red Shift Discovery • Hubble examined the light from stars in the distant galaxies. • He found that the pattern of spectral lines of the elements was shifted toward the red end of the spectrum. • Red Shift = Objects that are moving away • Blue Shift = Objects that are moving toward us

37. Hubble’s Conclusion Hubble concluded that if stars in distant galaxies were moving away from us (as evidenced by the red shift of their spectral lines), then the universe is expanding.

39. Doppler Effect:Sound and Light Waves When an object is moving away from us, any energy waves emitted will be stretched out to form longer, lower energy waves. Any object moving towards us would produce the opposite effect —shorter, higher energy waves. Thus, a siren is louder when it is moving toward you and is emitting short, high energy waves.

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